1. Field of the Invention
The present invention relates generally to electronic key systems and, more specifically, to a fault tolerant method of decoding an electronic key system.
2. Description Of the Related Art
It is known to control electronic equipment via an input key system which has a plurality of keys or switches arranged in any number of rows and columns. Such electronic equipment may include, for example, electronic calculators or radio receivers. The keys, when actuated, serve to establish electrical connections between input leads which may be associated with the aforementioned rows and columns and a microprocessor for data-processing information offered via the actuated keys in a binary code.
For a radio receiver in an automotive vehicle, the keys are typically a push-button switch such as, for example, a simple momentary switch acting as an operating contact. Each push-button switch is typically a rubber pad with conductive material to make contact with a printed circuit board. Although this electronic key system has worked well for the radio receiver, it suffers from the disadvantage that the conductive material wears off over time and sticks to the printed circuit board causing a shorted switch contact. Mechanical features such as stuck keys have also caused switch contact shorts. Another disadvantage of this electronic key system is that typical key decoding locks up all keys if any key or keys become shorted.